Raw acetonitrile is a by-product of the
manufacture of acrylonitrile. It is co-polymerised
with butadiene and styrene to make ABS, a
plastic used in cars etc, and the market for it has
collapsed over the last six months. Hence so has
the production of acetonitrile. There are no
manufacturing plants to make acetonitrile
(unlike THF or methanol) and there is little
prospect of one being built. Stocks are now
depleted, and hence those distilling it for use in
HPLC can no longer get enough supplies.
Acetonitrile is now being offered at extortionate
prices. In the short term, this means that we will
all have less, if any, acetonitrile available to us,
and when it does come back on stream, it could
be a lot more expensive.
Many HPLC methods use acetonitrile as part of
the mobile phase. It is an excellent eluent. It
has low viscosity, good selectivity, 100%
miscibility with water, reasonable buffer
solubility, and is almost transparent to UV light.
HPLC methods are usually validated (checked
thoroughly to ensure that correct results are
obtained even if small changes to the operating
conditions apply) and are sometimes registered.
Validation can take up to three months,
registration can take much longer, and both are
expensive. So once a method is set in concrete,
it is almost impossible to change. However...
if the acetonitrile specified in the method
ceases to be available, it is necessary at some
point to bite the bullet, and make the decision
to change the method.
There are two approaches. The first is to do the
absolute minimum necessary to get the
separation to work with another solvent, and
re-register as fast as possible. This has obvious
attractions in the short term, in terms of time,
cost, and ease of re-registration. The
alternative is to use this as a once in a lifetime
opportunity to redevelop the method using
modern columns etc, and to check again that
the most appropriate temperature, pH, buffer
concentration is being used. It takes longer, but
in time to come, with the benefit of hindsight,
this can seem a much wiser approach.
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